The prior art dealing with catalytic cracking catalysts is voluminous with a basic underlying goal being the preparation of modified zeolites for use as cracking catalysts. These zeolites are then added to alumina, silica, etc. as a matrix for the zeolite. The zeolitic component has generally been zeolite Y and has essentially been unchanged for over a decade. The development of the art of cracking catalysts has centered, for the most part, on preparing catalyst formulations by employing pretreated zeolites which are then subsequently admixed with various matrices. Representative of such developments are those disclosed in U.S. Pat. Nos. 3,140,249, 3,352,796, 3,312,615 and 3,542,670.
Another approach has been related to various secondary treatments for zeolites, such as processes to lower the alkali metal content of the basic zeolitic component (e.g., U.S. Pat. No. 3,293,192 and U.S. Pat. No. Re. 28,629) and processes to extract aluminum from the zeolitic framework (to enhance the thermal stability of the zeolite). Of course the latter processes necessarily result in products having sites where aluminum has been removed, and accordingly, the zeolites formed by such a process having certain instability as a result.
In EPC Application No. 81110620.3, having EPC Publication No. 82.211 and published June 29, 1983, incorporated herein by reference thereto, a new class of zeolites is disclosed and denominated therein as zeolite "LZ-210". This class of aluminosilicates comprises aluminosilicates having a chemical composition expressed in terms of mole ratios of oxides as: EQU (0.85-1.1)M.sub.2/n O:Al.sub.2 O.sub.3 :x SiO.sub.2
wherein "M" is a cation having the valence "n", and "x" has a value greater then 6.0. LZ-210 is a new class of aluminosilicates having a faujasite structure and having an SiO.sub.2 to Al.sub.2 O.sub.3 ratio greater than 6.0 while not having the problems necessarily associated with dealuminated, i.e., aluminum extracted, zeolites.
Among the various prior art processes are processes involving the treatment of zeolites with halogen-containing compounds whereby residual fluoride is provided to the zeolite. Representative of patents for such processes are U.S. Pat. Nos. 3,620,960 (molybdenum fluoride); 3,630,965 (hydrofluoric acid); 3,644,220 (volatile halides selected from the group consisting of aluminum, zirconium, titanium, tin, molybdenum, tungsten, chromium, vanadium, antimony, bismuth, iron, platinum group metals and rare earths): 3,575,887 (fluorides and chlorides); 3,699,056 (halogenated hydrocarbons) 3,702,312 (fluorides and chlorides); 4,427,788 (ammoniacal aluminum fluoride solution for treatment of zeolites having a silica-to-alumina ratio greater than 100); and 4,427,790 (complex fluoranion treatment of zeolites having a silica-to-alumina ratio greater than 100).
U.S. Pat. No. 4,427,790 is a recent patent disclosing that certain fluoroanions provide enhancement in the activity of crystalline zeolites, but only when the zeolites have silica-to-alumina ratios greater than about 100. The patent also discloses the post-admixture of such treated products with matrix materials. Interestingly, the patent affirmatively teaches that the process is beneficial only for the treatment of such high silica zeolites and only when such zeolites are treated in the absence of any other component.
One variation of the above fluoride treatments for zeolites is disclosed in U.S. Pat. No. 3,619,412. The process of U.S. Pat. No. 3,619,412 comprises the treatment of a mixture of mordenite and amorphous silica-alumina with a solution of a fluorine compound such as ammonium difluoride or hydrofluoric acid. The hydrofluoric acid treatment is said to provide stability to the treated catalyst. Further, processes involving specific treatments of zeolites having silica-to-alumina ratios greater than 100 are disclosed in U.S. Pat. Nos. 4,427,786; 4,427,787; 4,427,789 and 4,427,791. U.S. Pat. No. 4,427,786 discloses the treatment of supported zeolites, wherein the zeolite has a silica-to-alumina ratio greater than 100, with boron fluoride, hydrolyzing of the boron fluoride, an ammonium salt exchange and calcination. A comparison of examples 2 and 9 therein shows that the activity of zeolites having a silica-to-alumina ratio of less than 70 showed a decrease in activity as a result of the process. U.S. Pat. No. 4,427,787 discloses the treatment on an alumina-supported zeolite, said zeolite having a silica-to-alumina ratio greater than 100, with a dilute aqueous solution of hydrogen fluoride. The hydrogen fluoride treatment is said to preferentially increase the activity of zeolites having silica-to-alumina ratios over 100. U.S. Pat. No. 4,427,789 discloses the treatment of an alumina-supported zeolite, said zeolite having a silica-to-alumina ratio greater than 100, with an aqueous solution of an alkali metal fluoride, impregnation with a warm solution of an ammonium salt and a calcination. U.S. Pat. No. 4,427,791 discloses a process for the treatment of an inorganic oxide material with ammonium fluoride or boron trifluoride, ammonium exchange, and calcination. The treatment is said to enhance the activity of the inorganic oxide material as a result of the ammonium exchange step.
The use of LZ-210 and forms of LZ-210 as catalysts is disclosed in copending and commonly assigned U.S. Ser. No. 490,965, filed May 2, 1983 and U.S. Ser. No. 500,446, filed June 2, 1983.
The instant invention relates to a new process wherein a large pore zeolite in combination with at least one inorganic oxide matrix component is contacted with specific fluoro salt solutions or slurries having a pH greater than 7, as discussed hereinafter, to provide catalysts useful in hydrocarbon conversion processes.